Scent boxes and carousels are used for imprint training. The principle difference is scents boxes can be placed in random search patters in different terrains. They work hand in hand with the carousel training and offer the trainer variety in the training program.
Imprint training may start with a piece of tennis ball hidden inside a training box alongside the target odour. Very soon the dog will associate the reward with the target.
A lot of trainers use training boxes with puppies and younger dogs. Generally, these devices are much lower to the ground and work well with young animals. This can also help lead young dogs into carousel training.
Training boxes also help to introduce background smells away from the compound or general training area when taken in operational search environments.